Headsets are a popular device for delivering sound to one or both ears of a user, such as playback of music or audio files or telephony signals. Headsets typically also capture sound from the surrounding environment, such as the user's voice for voice recording or telephony, or background noise signals to be used to enhance signal processing by the device. Headsets can provide a wide range of signal processing functions.
For example, one such function is Active Noise Cancellation (ANC, also known as active noise control) which combines a noise cancelling signal with a playback signal and outputs the combined signal via a speaker, so that the noise cancelling signal component acoustically cancels ambient noise and the user only or primarily hears the playback signal of interest. ANC processing typically takes as inputs an ambient noise signal provided by a reference (feed-forward) microphone, and a playback signal provided by an error (feed-back) microphone. ANC processing consumes appreciable power continuously, even if the headset is taken off.
Thus in ANC, and similarly in many other signal processing functions of a headset, it is desirable to have knowledge of whether the headset is being worn at any particular time. For example, it is desirable to know whether on-ear headsets are placed on or over the pinna(e) of the user, and whether earbud headsets have been placed within the ear canal(s) or concha(e) of the user. Both such use cases are referred to herein as the respective headset being “on ear”. The unused state, such as when a headset is carried around the user's neck or removed entirely, is referred to herein as being “off ear”.
Previous approaches to on ear detection include the use of dedicated sensors such as capacitive, optical or infrared sensors, which can detect when the headset is brought onto or close to the ear. However, to provide such non-acoustic sensors adds hardware cost and adds to power consumption. Another previous approach to on ear detection is to provide a sense microphone positioned to detect acoustic sound inside the headset when worn, on the basis that acoustic reverberation inside the ear canal and/or pinna will cause a detectable rise in power of the sense microphone signal as compared to when the headset is not on ear. However, the sense microphone signal power can be affected by noise sources such as wind noise, and so this approach can output a false positive that the headset is on ear when in fact the headset is off ear and affected by noise. These and other approaches to on ear detection can also output false positives when the headset is held in the user's hand, placed in a box, or the like.
Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
In this specification, a statement that an element may be “at least one of” a list of options is to be understood that the element may be any one of the listed options, or may be any combination of two or more of the listed options.